Biology and Ecology of Species

European beaver (Castor fiber L.) is a semiaquatic animal and is the biggest rodent of the northern hemisphere. Grown-up males are between 75-95cm long, 30cm of which is the tail. They can weigh up to 20-30kg. Its thick set dark brown body makes it an excellent swimmer and diver. It is active during the night. The back is bent, the neck is short and thick, the head wide, narrowing towards the snout, the forehead is flat with a short snout. The legs are short, firm, the rear ones are slightly longer than the front ones with 5 toes each. It has got webbed rear feet. The tail is clearly parted from the body, circular in the root, straight in the middle and flat towards the top where it is about 20 cm wide. The ears are long, small and usually hidden in the fur. The eyes are small with mobile eyelids. Beaver fur consists of thick silky hairs about 5cm long. Fur is oily and thick so that it can prevent water from touching the skin and keeps body temperature stabile. The colour of fur is dark brown with gray shades on the back and the belly is brighter. Beaver can be recognized by its very big, strong, flat, smooth front teeth and looking from aside they look like a chisel sticking out from the jaw. Both sexes have mating glands on the lower part of the belly near the anus (“castoreum”) which have strong smell and bitter taste. Secretion of these glands was often used as balsam for alleviating pain caused by convulsions. This monogamous herbivore eats barks and leaves of various trees, but mostly willows. Its special treat is soft upper part of branches and shoots, while from older trees it is bark it eats. Sometimes it eats grass near the river banks. It is sexually mature at the age of 2-3 years. Mating period is from February to March and a female carries its young for 107 days and brings forth 1-5 young which can see 8-10 days after the birth when their mother takes them into the water with her. Life expectancy is up to 20 years. Its hiding place is in the water under the hummock of branches. If the level of water is low beaver will make a dam to maintain the necessary level of water. With beaver as with most other animals, it is female that builds a hiding place while male is only an obedient worker. Both male and female work during the year and in the summer and at the beginning of autumn they play more than they build. It is interesting what Fizinger noticed about beaver’s behaviour before the storm. A few hours before the storm it starts checking the building (the hummock or dam), fixing it and, if necessary, bringing more branches and leaves in front of the entrance. Beaver’s hummock has one or several entrance halls 2-6m long which can be entered bellow the water surface. The hummock itself has one big room, whose floor is covered with splinters, and a few storerooms. Each hummock has its emergency exit in the hidden parts of the woods connected with underground holes.